1. Field of the Invention
The present invention relates to a malfunction detection device for a hot water supplier (i.e. a water heater).
2. Background Art
A conventional heat pump hot water supplier has, as shown in FIG. 3, a heat pump unit 1 and a tank unit 2 storing hot water heated by the heat pump 1. The tank unit 2 includes, as shown in FIG. 1 showing an embodiment of the present invention, a hot water storage tank 3, a circulation path 12 connected with the hot water storage tank 3, and a heat exchanger path 14 interposed in the circulation path 12, and is capable of heating the heat exchanger path 14 by a heat pump heating source, boiling tepid, or low temperature water which has flowed out from the hot water storage tank 3 to the circulation path 12, and returning the boiled water to the hot water storage tank 3. Hot water stored in the hot water storage tank 3 is supplied to a bath and other places which are not shown in the figure.
The hot water storage tank 3 is provided with a feed water port 5 on its bottom wall, and with a hot water outlet 6 on its top wall. Tap water is supplied into the hot water storage tank 3 through the feed water port 5 and high temperature hot water is discharged from the hot water outlet 6. Furthermore, the hot water storage tank 3 is provided with a water intake 10 in an open condition on its bottom wall, and with a hot water inlet 11 in an open condition on the upper part of its side wall (peripheral wall). The water intake 10 and the hot water inlet 11 are connected by the circulation path 12. Provided in the circulation path 12 are a water circulating pump 13 and the heat exchanger path 14. A feed water flow path 8 is connected with the feed water port 5.
By the way, the hot water storage tank 3 is provided with four residual hot water quantity detectors 18a, 18b, 18c, and 11d vertically arranged in a predetermined pitch, and with a temperature detector 19a constituting a feed water temperature detecting section 19. Each of the residual hot water quantity detectors 18a, 18b, 18c, and 18d and the temperature detector 19a is constituted by, for example, a thermistor. Furthermore, the circulation path 12 is provided with an incoming water thermistor 20a, which serves as an incoming water temperature detecting section 20, upstream of the heat exchanger path 14, and with a discharged hot water thermistor 21a, which serves as a discharged hot water temperature detecting section 21, downstream of the heat exchanger path 14.
The circulation path 12 includes incoming water piping 15 and discharged hot water piping 16. The incoming water piping 15 consists of first piping 15a on the hot water storage tank 3 side in which the pump 13 is interposed, second piping 15b on the heat source side in which the incoming water thermistor 20a is interposed, and connecting piping 15c coupling (connecting) the first piping 15a and the second piping 15b. The discharged hot water piping 16 consists of first piping 16a on the hot water storage tank 3 side, second piping 16b on the heat source side in which the discharged hot water thermistor 21a is interposed, and connecting piping 16c coupling (connecting) the first piping 16a and the second piping 16b Connection of the connecting piping 15c and 16c is established at a site as described later.
The heat pump unit (heating source) 1 includes a refrigerant circuit which is constituted by a compressor 25, a water heat exchanger 26 constituting the heat exchanger path 14, a motor-operated expansion valve (decompression mechanism) 27, and an air heat exchanger (evaporator) 28 which are connected in this order. In other words, a discharge pipe 29 of the compressor 25 is connected with the water heat exchanger 26, the water heat exchanger 26 is connected with the motor-operated expansion valve 27 by a refrigerant path 30, the motor-operated expansion valve 27 is connected with the evaporator 28 by a refrigerant path 31, and the evaporator 28 is connected with the compressor 25 by a refrigerant path 33 in which an accumulator 32 is interposed. With this arrangement, when the compressor 25 is driven, water flowing in the heat exchanger path 14 is heated by the water heat exchanger 26. Furthermore, a fan 34 adjusting the ability of the evaporator 28 is added to the evaporator 28.
According to the hot water supplier configured as described above, when the compressor 25 is driven and the water circulating pump 13 is driven (operated), stored water (low temperature water) flows from the water intake 10 provided at the bottom of the hot water storage tank 3 and then flows through the heat exchanger path 14 of the circulation path 12. At that time, this water is heated (boiled) by the water heat exchanger 26 and returned to the upper part of the hot water storage tank 3 through the hot water inlet 11. Such operations are performed continuously and thereby high temperature hot water can be stored in the hot water storage tank 3. During the operation of the hot water supplier, discharge pipe control is performed which adjusts the degree of opening, etc. of the motor-operated expansion valve 27 to match the discharge pipe temperature of the compressor 25 to a target discharge pipe temperature. Since a mid night electricity unit rate is set lower than a daytime electricity unit rate in a present electricity rate system, this operation is performed mainly in a midnight time period (for example, a time period from 23:00 to 7:00) during which an electricity unit rate is low. Such a heat pump hot water supplier is known from, for example, JP 2003-222406 A.
In addition, an excessive temperature rise preventer (bimetal thermostat) 50 is mounted on the top of the hot water storage tank 3 as shown in FIG. 3 in order to prevent various malfunctions from occurring due to an abnormal temperature rise of hot water in the hot water storage tank 3. An application example of such an excessive temperature rise preventer (bimetal thermostat) 50 is known from, for example, JP 2000-39144 A or JP 11-108417 A.
In the hot water supplier, when a temperature detected by the discharged hot water thermistor 21a exceeds a predetermined temperature or when the temperature of the top of the hot water storage tank 3 increases and the excessive temperature rise preventer (bimetal thermostat) 50 operates, the compressor 25 is shut down from the viewpoint of securing safety. In other words, in the conventional hot water supplier, a power supply is connected, as shown in FIG. 3, to a power supply unit 52 of the heat pump unit 1 through a tank printed circuit board 51 of the tank unit 2, and the power supply unit 52 supplies power to a heat pump control section 53. The heat pump control section 53 is for controlling the drive frequency of the compressor 25 and the degree of opening of the motor-operated expansion valve 27. By the operation of the bimetal thermostat 50, a power supply line 54 between the tank printed circuit board 51 and the power supply unit 52 is shut off. The reference numeral 55 denotes a tank control section.
However, the fact is that the excessive temperature rise preventer (bimetal thermostat) 50 is very expensive and cannot sufficiently respond to a request of equipment cost down.